The invention relates to a method for the preparation of essentially homogeneous, compressed gas mixtures with SF.sub.6, and to a mixing station, particularly a mobile mixing station, which can be used for this purpose.
In principle, separate gases can be converted into a homogeneous gas mixture by transferring the gases into a container and waiting for a sufficiently long period of time, until a corresponding homogeneous gas mixture is formed by diffusion. However, since extremely long times are required for this purpose, such a method cannot be used industrially. Of course, mixing is also observed when gas streams are passed into a stationary mixer and/or into a common pipeline. In such a case however, mixing is not always so thorough, that the mixtures achieved can be considered to be "homogeneous", especially if gases of greatly different densities, such as those containing SF.sub.6, are to be mixed. Such a gas mixture is the mixture of SF.sub.6 (sulfur hexafluoride) and N.sub.2 (nitrogen). As a gas, SF.sub.6 has a density of 6.18 g/l and N.sub.2 a density of 1.170 g/l, in each case determined at a temperature of 15.degree. C. and a pressure of 1 bar absolute (normal conditions in the sense of this application). Such gas mixtures are used, for example, as an insulating gas for underground cables carrying a current. In this connection, it is a particular problem that the gas mixtures (which are required in large quantities) expediently must be prepared on site. If namely gas mixtures, pre-fabricated in a factory, are to be used, these mixtures would have to be transported in gas cylinders under a high pressure in order to keep the transporting costs as a low as possible; however, this is not possible, since a portion of the SF.sub.6 would then condense and corresponding demixing would occur.